1. Field of the Invention
The present invention relates generally to a medical device for placing an embolic coil at a preselected location within a vessel of the human body. More particularly, the present invention relates to a catheter system having a distal tip for retaining an embolic coil in order to transport the coil to a preselected position within the vessel and a control mechanism for releasing the embolic coil at the preselected position.
2. Description of the Prior Art
For many years, flexible catheters have been used to place various devices within the vessels of the human body. Such devices include dilation balloons, radiopaque fluids, liquid medications, and various types of occlusion devices like balloons and embolic coils.
In the case of balloon catheters, prior to introducing the catheter into a human body, it is desirable to purge air from the catheter with a liquid to prevent the air from being introduced into blood vessels. In the past, purging the catheter involved inflating the balloon section of the catheter to allow the air to escape out of the distal end of the balloon and then providing some mechanism to prevent air from reentering the balloon while it is being deflated.
U.S. Pat. No. 5,728,065 to Follmer, et al., discloses a balloon catheter with a vent hole disposed near the distal end of the balloon. The vent hole normally lays against the surface of an inner tubular member, preventing gases from entering the balloon. During purging, the balloon is inflated, the distal end of the balloon opens exposing the vent hole, and gases and a portion of the inflation medium flow out.
U.S. Pat. No. 4,811,737 to Rydell, discloses a balloon catheter with a slit in the distal portion of the tubular member. Fluid is injected into the catheter and flows through multiple inflation ports to expand the balloon. The purging fluid forces the air within the balloon through the slit in the tubular member.
U.S. patent application Ser. No. 09/400,680 to Barry, et al., entitled, xe2x80x9cHeated Vascular Occlusion Coil Deployment System,xe2x80x9d filed Sep. 21, 1999; U.S. patent application Ser. No. 09/399,714 to Barry, et al., entitled, xe2x80x9cEmbolic Coil Deployment System With Retaining Jaws,xe2x80x9d filed Sep. 21, 1999; U.S. patent application Ser. No. 09/177,848 to Hieshima, entitled, xe2x80x9cEmbolic Coil Hydraulic Deployment System,xe2x80x9d filed Oct. 21, 1998; U.S. patent application Ser. No. 09/256,161 to Lulo, entitled, xe2x80x9cEmbolic Coil Deployment System With Improved Embolic Coil,xe2x80x9d filed Feb. 22, 1999; U.S. patent application Ser. No. 09/256,163 to Diaz, et al., entitled, xe2x80x9cEmbolic Coil Deployment System With Improved Embolic Coil,xe2x80x9d filed Feb. 22, 1999; U.S. patent application Ser. No. 09/258,678 to Goodson, et al., entitled, xe2x80x9cEmbolic Coil Hydraulic Deployment System With Improved Syringe Injector,xe2x80x9d filed Feb. 25, 1999; and U.S. patent application Ser. No. 09/257,742 to Lulo, et al., entitled, xe2x80x9cEmbolic Coil Hydraulic Deployment System Having Improved Catheter,xe2x80x9d filed Feb. 24, 1999, are all assigned to the same assignee as the subject application and disclose embolic coil deployment systems for use in deploying an embolic device at a predetermined location within a vessel.
In accordance with the present invention, there is provided a vascular occlusive coil deployment system for use in placing a coil at a preselected site within a vessel including a catheter having a tubular wall and having a lumen extending throughout the length of the catheter. The catheter further includes a proximal section and a distal section. The distal section of the catheter is formed from a material which exhibits the characteristic that the wall of the distal section of the catheter expands outwardly when a liquid is applied within the lumen of the catheter. A syringe is coupled to the proximal section of the catheter for applying the liquid within the lumen of the catheter. The proximal end of an embolic coil is disposed in fluid-tight engagement within the lumen of the distal section of the catheter. When the liquid is applied within the lumen of the catheter, the wall of the distal section of the catheter expands outwardly and the proximal end of the embolic coil is released. At least one aperture is included for purging air from the lumen of the catheter to prevent the air from being introduced into the blood vessels. The aperture extends radially through the wall of the distal section of the catheter at a point proximal to the proximal end of the embolic coil. The aperture is sized such that air can pass through the aperture when fluid pressure is applied to the interior of the catheter but the flow of more viscous fluids is highly restricted.
In accordance with another aspect of the present invention, there is provided a vascular occlusive coil deployment system for use in placing a coil at a preselected site within a vessel including a catheter having a tubular wall and having a lumen extending throughout the length of the catheter. The catheter further includes a proximal section and a distal section. The distal section of the catheter is formed from a material which exhibits the characteristic that the wall of the distal section of the catheter expands outwardly when a liquid is applied within the lumen of the catheter. There is also provided a means for applying the liquid within the lumen of the catheter. The proximal end of an embolic coil is disposed in fluid-tight engagement within the lumen of the distal section of the catheter. When the liquid is applied within the lumen of the catheter, the wall of the distal section of the catheter expands outwardly, and the proximal end of the embolic coil is released. Finally, the vascular occlusive coil deployment system includes a means for purging air from the system.
In accordance with another aspect of the present invention, the means for applying a fluid pressure within the lumen of the catheter comprises a syringe coupled to the proximal section of the catheter.
In accordance with another aspect of the present invention, the purging means comprises at least one aperture extending radially through the wall of the distal section of the catheter at a point just proximal to the proximal end of the embolic coil.
In accordance with another aspect of the present invention, the aperture is sized such that the outflow is highly restricted for liquids having a viscosity greater than about 1xc3x9710xe2x88x928 lbxc2x7s/in2.
In accordance with another aspect of the present invention, the aperture is sized such that the highly restricted outflow of liquid produces a fluid pressure within the lumen of the distal section of the catheter of at least 250 psi.
In accordance with another aspect of the present invention, the aperture is circular and has a diameter between approximately 0.00095 inches and 0.0012 inches. Preferably, the diameter is approximately 0.001 inches.
In accordance with another aspect of the present invention, the aperture is located between about 0.003 inches and 0.006 inches from the proximal end of the embolic coil.
In accordance with another aspect of the present invention, the liquid applied within the lumen of the catheter exerts a fluid pressure within the lumen of the proximal section of the catheter between about 50 psi and 125 psi and thereby causes air to pass through the aperture in the distal section of the catheter.
In accordance with still another aspect of the present invention, the proximal section of the catheter and the distal section of the catheter are formed from substances with different durometers. The distal section is formed from a material having a durometer which is substantially lower than the durometer of the material used to form the proximal section. The proximal section of the catheter is formed from a polymer having a durometer between 62 D to 75 D and the distal section of the catheter is formed from a polymer having a durometer between about 25 D and 55 D. Preferably, the proximal section of the catheter is formed from a material having a durometer of about 75 D and the distal section of the catheter is formed from a material having a durometer of about 40 D.
In accordance with another aspect of the present invention, the liquid is formed of saline solution. Preferably, the saline solution includes about 0.9% sodium chloride.